OBJECTIVES: 1). Futile Cycles in Glucose Metabolism in Rat Hepatocytes. a) The recycling between glucose and glucose 6-P will be determined by using 2-T glucose and 2-T galactose by two independent procedures. b) Recycling between fructose 6-P and fructose 1,6-P2 will be quantitated from the randomization of 14C from 1-14C galactose in glucose. c) The rate of the pyruvate kinase during active gluconeogenesis will be measured using a recently described method. d) The effect of dietary status, hormones and ethanol on these 3 cycles will be studied. 2). The rate of fructose 1,6-diphosphatase and recycling between fructose 6-P and fructose 1,6-P2 will be established in slices and acini from mammary gland of lactating rats. 3). Glycogen Metabolism. The mechanism of the stimulation of glycogen synthesis by glutamine will be studied. The effect of amino acids and other nitrogen compounds on the activities of the enzymes of glycogen metabolism will be determined. 4). The mechanism of the stimulatory effect on lactate uptake and oxidation, and glucose synthesis in rat hepatocytes will be studied. BIBLIOGRAPHIC REFERENCES: Estimation of glucose turnover and recycling in rabbits using (3H, 14C) glucose labels. A. Dunn, J. Katz, S. Golden and M. Chenoweth. Am. J. Physiol. 230, 1159-1162, 1976. Effects of hormones and of ethanol on the fructose 6-P-fructose 1,6-P2 futile cycle during gluconeogenesis in the liver. R. Rognstad and J. Katz. Arch. Bioch. Biophys. 177, (October), 1976.